Sur d’autres sites (6340)

• avutil/float_dsp : Unavpriv avpriv_scalarproduct_float_c()

  15 mars, par Andreas Rheinhardt

  avutil/float_dsp : Unavpriv avpriv_scalarproduct_float_c()
  Not worth the overhead of exporting it.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavcodec/Makefile
  • [DH] libavcodec/acelp_pitch_delay.c
  • [DH] libavcodec/acelp_vectors.c
  • [DH] libavcodec/float_scalarproduct.c
  • [DH] libavcodec/qcelpdec.c
  • [DH] libavcodec/ra288.c
  • [DH] libavcodec/sipr.c
  • [DH] libavcodec/sipr16k.c
  • [DH] libavcodec/wmavoice.c
  • [DH] libavutil/Makefile
  • [DH] libavutil/float_dsp.c
  • [DH] libavutil/float_dsp.h
  • [DH] libavutil/float_scalarproduct.c

• FFMpeg delay while streaming RTSP Stream

  15 mars 2024, par Vikrant

  What the code is doing ?

  


  

  • Collecting live frames from IP camera, adding date-time on the frame using OpenCV.

  


  • Using cv2.imshow('preview',frame), we display live feed.

  


  • Now same frame(s) are also sent to other RTSP Server on port 8554 using FFMpeg

  


  


  Using the code

  


  

  • Using VLC, FFMPEG Stream is visible with date-time over it.

  


  


  Why I am doing this ?

  


  

  • To create a custom RTSP stream with modifications over camera feed.

  


  


  Defining Issue :

  


  There is around 3-4 seconds delay / latency in the stream on VLC via FFMpeg as compared to original preview using OpenCV imshow.

  


  Following is the code :

  


  import cv2
import subprocess
import threading
import datetime

rtsp_width = 1280
rtsp_height = 720

#system stream
rtsp_url = "rtsp://ip_address:8554/system/cam_preview" 

command = ['ffmpeg',
        '-fflags', 'nobuffer',
        '-flags', 'low_delay',
        '-loglevel' , '0',   
        '-analyzeduration', '0', 
        '-re',
        '-y',
        '-init_hw_device', 'cuda:0',
        '-hwaccel', 'cuda',
        '-hwaccel_output_format', 'cuda',    
        '-f', 'rawvideo',
        '-vcodec', 'rawvideo',
        '-pix_fmt', 'bgr24',
        '-s', "{}x{}".format(rtsp_width, rtsp_height),             
        '-r', "15",
        '-an',                  
        '-i', '-',   
        '-g', '15',    
        '-c:v', 'h264_nvenc',
        '-use_wallclock_as_timestamps', '1',
        '-f', 'rtsp',     
        '-rtsp_transport','tcp',
        str(rtsp_url)]
    
print("MAIN > RTSP URL:", str(rtsp_url))

process = subprocess.Popen(command, stdin=subprocess.PIPE)

#camera rtsp url
path = "rtsp://username:password@ip_address/axis-media/media.amp" 

cap = cv2.VideoCapture(path)

def read_frames():
    global process

    while True:
        if cap.grab():
            ret, frame = cap.retrieve()
            if ret:    
                date_format = '%Y-%m-%d %H:%M:%S'
                today_str = datetime.datetime.now().strftime(date_format)
                cv2.rectangle(frame, (445,5), (580,20), (0,0,0), -1)
                cv2.putText(frame,today_str,(450,15), cv2.FONT_HERSHEY_SIMPLEX, 0.35, (255, 255, 255), 1 )                      
                process.stdin.write(frame.tobytes())
                cv2.imshow('preview',frame)
            else:
                print("Error grabbing frame")
                cap.release()
                process.kill()
                cv2.destroyAllWindows()           
                break
        if cv2.waitKey(1) & 0xFF == ord('q'):
            cap.release()
            process.kill()
            cv2.destroyAllWindows()
            break

thread = threading.Thread(target=lambda: read_frames())
thread.start()


  


  Things to note

  


  cv2 package is compiled with CUDA ARCH 7.5

  


  Following are some FFMpeg research parameters :

  


     '-fflags', 'nobuffer',

   '-flags', 'low_delay',

   '-tune', 'zerolatency'


  


  Few others, but they did not made any impact over latency, on average about 4 seconds of delay might worth be reducing, for applications like motion-tracking, object-detection.
How to reduce this latency ?

  


• How To Call JAVA Methods from inside of a Thread in JNI

  16 novembre 2019, par Falcuun

  TL ;DR ; I’m having a problem with passing my FFMPEG raw data from C++ code to JAVA code, for displaying, through a thread.

  There is a server set up that sends out encoded frames to its clients. Those encoded frames are encoded with some FFMPEG magic. When received on client side, the fore-mentioned frames are getting decoded into raw RGB data (as a unsigned char *). The problem now is that frames are being received in a "listener" of sorts. Just a thread running in the background polling the server and running specific onFrame function once a new frame is available.

  The current solution for displaying the frames in a video-format is to save each frame to internal storage in C++, and then have a FileObserver on java side that displays an image as soon as it’s written in the memory. Sadly, that approach yields a 6 FPS video on phone, for a 10 FPS video from Server.

  I need a way of passing that unsigned char * (jbytearray) to my JAVA code so I can decode it and display it from RAM rather than Disk.

  It’s worth mentioning that onFrame function cannot have JNIEnv* && jobject inside it’s arguments list (Library requirements).

  What I have tried so far is making a native method in my MainActivity through which I pass JNIEnv and jobject and assign those to global variables

  JNIEnv* m_globalEnv = env;
  
  jobject m_globalObject = thiz;
  
  JavaVM m_jvm = 0;
  
  jclass mainActivity = m_globalEnv->GetObjectClass(m_globalObject);
  
  jmethodID testMethod = m_globalEnv->GetMethodID(mainClass, "testMethod", "(I)V");
  
  
  
  m_globalEnv->GetJavaVM(&m_jvm);

  After that, in my onFrame I call
  jvm->AttachCurrentThread(&m_globalEnv, NULL);
  And then I try to call a JAVA method from somewhere inside the code (It’s irrelevant where/when in the onFrame I call it) by doing :

  m_globalEnv->CallVoidMethod(m_globalObject, "testMethod", 5);

  And then all crashes with either :

  1- JNI DETECTED ERROR IN APPLICATION: use of invalid jobject 0xffe8ea7c
  
  2- JNI DETECTED ERROR IN APPLICATION: Thread is making JNI calls without being attached
  
  .
  
  .
  
  .

  EDIT 1

  After Trying out the code from Michael’s solution, I got the
  java_vm_ext.cc:542] JNI DETECTED ERROR IN APPLICATION: use of invalid jobject 0xc94f7f8c error.
  After running the app in debug mode to catch the error, I got to the jni.h ; Line of code that triggers the error is :
  m_env->CallVoidMethod(m_globalObject, testMethod, 5);
  (5 being the number I am trying to pass for testing purposes).
  The line of code inside jni.h that is being highlighted by the debugger is inside of
  void CallVoidMethod(jobject obj, jmethodID methodID, ...)
  and it’s
  functions->CallVoidMethodV(this, obj, methodID, args);
  which is defined on line 228 :
  void (*CallVoidMethodV)(JNIEnv*, jobject, jmethodID, va_list);